Rack steering device

ABSTRACT

The invention relates to a rack and pinion steering device having a rack ( 1 ) which is arranged in a housing ( 4 ) and is connected at both ends to the steerable wheels via track rods ( 6 ) and steering arms, and having a pinion ( 2 ) which engages continuously in the rack ( 1 ) and is connected to the manual steering wheel via a steering column, and having stop means ( 10; 11; 12 ) which are integrated at both ends between the housing ( 4 ) and axially movable parts of the rack and pinion steering device and limit the axial movement of the rack ( 1 ) in both steering directions, the stop means ( 10; 11; 12 ) comprising elastically compliant material ( 12 ) which is completely enclosed in nonelastic parts ( 10; 11 ) of the stop means ( 10; 11; 12 ) which can move axially with respect to one another.

[0001] The invention relates to a rack and pinion steering deviceaccording to the precharacterizing clause of patent claim 1.

[0002] It is generally known in rack and pinion steering devices for thesteering to be limited by the wheel support (steering knuckle) strikingthe suspension link or by the limiting means being moved into thesteering mechanism. These steering limiting systems display disruptingimpact noises.

[0003] Said impact noises are avoided in a rack and pinion steeringdevice according to DE 34 29 597 A1, which has stop members which arefastened to the rack in order to limit the axial movement of the rackagainst the housing. A part of the contact faces is equipped withelastically compliant parts in such a way that contact is initially madewith the elastically compliant parts, in order to absorb the impact joltin this way, before the metal on metal contact occurs.

[0004] JP 08 133102 A has disclosed a stop system whose stop means,comprising elastic material, is completely enclosed in mutually axiallymovable, nonelastic parts of the stop system, faces of a support elementof the steering device being partially used for the enclosure.

[0005] In particular in the case of electrically assisted steeringdevices in which the rotational output movement of an electric motor isused to assist the manual force exerted on the steering handle, thedamping concepts of conventional stop systems are not sufficient, onaccount of the mass moment of inertia of the electric motor, to damp theimpact noises between the pairs of stops, for example the track rod andsteering mechanism housing.

[0006] The invention specified in patent claim 1 is based on the problemof designing a rack and pinion steering device of the type specified inthe introduction, in which satisfactory displacement restriction isachieved, both for conventional steering systems and for power assistedor externally assisted steering systems, and disrupting contact noisesare avoided in the process. The problem is solved by the featuresspecified in the characterizing part of patent claim 1,

[0007] which satisfactory displacement restriction is achieved, both forconventional steering systems and for power assisted or externallyassisted steering systems, and disruptive contact noises are avoided inthe process. The problem is solved by the features specified in thecharacterizing part of patent claim 1, in that the elastically compliantmaterial which is integrated between the pairs of stops is completelyenclosed by nonelastic parts of the stop means.

[0008] The advantages achieved by the invention consist, in particular,in sufficient limitation of the steering angle being made possible in asimple manner, without relatively great additional expenditure onmaterial and working time, and the stop means itself being designed tobe extremely simple and space saving. Advantageous developments of theinvention are specified in the dependent claims.

[0009] One exemplary embodiment of the invention is explained in greaterdetail in the following text and is shown in the drawing, in which:

[0010]FIG. 1 shows a section through a steering mechanism;

[0011]FIG. 1a shows a detail X;

[0012]FIG. 1b shows a further variant of the detail X.

[0013] Substantially identical parts in the different figures areprovided with identical designations.

[0014] The drawing shows a detail of a rack and pinion steering devicehaving a pair of stops 8; 9 and integrated stop means 10; 11; 12. Anequivalent system is arranged on the other side of the rack 1 for theopposite steering angle. The rack 1 extends in an axially movable mannerin a steering mechanism housing 4. A pinion 2 which is kept in constantengagement with the teeth of the rack 1 by a pressure piece 3 is mountedin an integrally formed attachment of the steering mechanism housing 4serving as pinion housing 5. As the manual steering wheel (not shown) isconnected to the pinion 2 via a steering column (not shown), themanually exerted steering force is transmitted to the rack 1 which,depending on the rotational direction of the pinion 2, transmits thesteering movement to the steerable wheels (not shown) at both ends viathe track rod 6 and the steering arm. The track rods 6 are in each caseconnected to the rack 1 via axial joints 7. Axial joint faces andhousing faces 8 and 9 form a pair of stops 8; 9 at both rack ends. Stopmeans 10; 11; 12 are integrated between the stop faces 8 and 9 of eachpair of stops 8; 9. A stop means 10; 11; 12 is formed from two flanges10; 11 (FIG. 1b) of different diameters which are arranged at a distancefrom one another in such a way that their short webs 10′ and 11′ in eachcase rest on the mutually facing side of the opposite long webs 10″ or11″ of the respective other flange 10 or 11, so that the flanges 10; 11form an approximately hollow-cylindrical chamber which completelysurrounds an elastically compliant material 12. While the outer flange11 is permanently installed in the housing 4, the inner flange 10 can bemoved axially to a limited extent. In another embodiment, the chamberfaces of the outer flange 11 are advantageously formed by an angularrecess 11 in the housing (FIG. 1a), so that the stop means 10; 11; 12 initself can be designed to be even more space saving.

[0015] The flange 10 which is arranged so as to be axially movable withrespect to the housing 4 maintains a distance, with its annular end face13 facing away from the axial joint 7 in the relieved state, from theaxially oriented face 14 of the housing 4. The faces 13; 14 which arearranged spaced apart and act as a mechanical end stop 13 and 14 protectthe enclosed elastically compliant material 12 against overstressing asa result of misuse.

[0016] This elastically compliant material 12 has undercuts 12′, bymeans of which the effect of the force introduced into this material 12by a steering maneuver is influenced in a targeted manner and itsdeformation is directed in predetermined directions (no gap extrusion).

[0017] By way of example, the elastically compliant material 12 isconnected directly to the housing 4 or with a form-fitting connection tothe outer flange 11 by an elastic snap-action connection. The material12 can also be fixed in position by an additional element, e.g. asecuring ring, or by calking, vulcanizing or adhesive bonding. As aresult of the permanent connection to the housing 4 or the flange 11,there are shear stresses on account of relative movements whichadditionally contribute to damping. Furthermore, the occurrence of gapextrusions in the elastic material 12 is avoided. It is likewisepossible for the flange 10 to be connected to the elastically compliantmaterial 12 using the same connecting elements or methods. By way ofexample, the flange 10 is connected to the material 12 by adhesivebonding. It is, however, also possible to insert the elastic material 12in one or more pieces into the chamber surrounding it without aform-fitting or force-transmitting connection.

[0018] In the exemplary embodiment shown, the steering mechanism housing4 is used as the support component 4 or 7 for the elastic stop means 10;11; 12, so that the face 8 which corresponds to the stop means 10; 11;12 is machined on the axial joint 7 of the track rod/rack connection.However, it is possible to integrate the elastic stop means 10; 11; 12on the axial joint 7 or the rack 1 itself and to integrate theoppositely oriented end face 9 on the housing 4.

[0019] Beyond the illustration of a conventional steering system, it isalso readily possible to use the elastic stop means 10; 11; 12 in powerassisted steering systems, such as hydraulic, pneumatic,electrohydraulic and electric or externally assisted steering systems,such as steer-by-wire steering operating with a steering mechanism, thatis to say the contact noises mentioned in the introduction and caused bythe mass moment of inertia of an electric motor used for steeringassistance are also eliminated.

1. A rack and pinion steering device having a rack which is arranged ina housing and is connected at both ends to steerable wheels via trackrods and steering arms, and having a pinion which engages continuouslyin the rack and is connected to the manual steering wheel via a steeringcolumn, and having stop means which are integrated at both ends betweenthe housing and axially movable parts of the rack and pinion steeringdevice and limit the axial movement of the rack in both steeringdirections, the stop means comprising elastically compliant materialwhich is completely enclosed in nonelastic parts of the stop means whichcan move axially with respect to one another, and faces of a supportcomponent of the steering device are partially used in order to enclosethe elastically compliant material, the elastically compliant materialin each case at one end being embedded in a recess of the supportcomponent of the steering mechanism and at the other end is surroundedby a flange which can move axially to a limited extent.
 2. (Canceled) 3.(Canceled)
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 5. (Canceled)
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 7. (Canceled) 8.(Canceled)
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 10. The rack and pinion steering device asclaimed in claim 1, wherein the stop means are integrated with thehousing at both ends and correspond with the end face of the axial jointof the track rod.
 11. The rack and pinion steering device as claimed inclaim 1, wherein the stop means are arranged on the track rod side andstrike against oppositely oriented end faces of the housing.
 12. Therack and pinion steering device as claimed in one of claims 1, 10 or 11,whereby in the relieved state of the stop means the face of the flangefacing away from the stop face maintains a distance from the face of thesupport component which corresponds with it.
 13. The rack and pinionsteering device as claimed in one of claims 1, 10 or 11, wherein theelastically compliant material has undercuts.
 14. The rack and pinionsteering device as claimed in one of claims 1, 10 or 11 wherein the stopmeans is adapted by additional elements and or displacement toward thesupport component or flange.
 15. The rack and pinion steering device asclaimed in one of claims 1, 10 or 11 wherein the flange is connected tothe elastically compliant material with a force-transmitting orform-fitting connection.